A 31-year-old woman presents with a rapidly enlarging barrel-shaped cervical mass and recent onset of weight loss. Serum sodium is 121 mmol/L. Biopsy shows sheets of small round blue cells with scant cytoplasm, nuclear moulding and perivascular crushing artefact. Immunohistochemistry is positive for synaptophysin and chromogranin. What is the most likely diagnosis?

• A Poorly differentiated squamous cell carcinoma
• B Small cell neuroendocrine carcinoma of the cervix ✓
• C Endometrioid adenocarcinoma of the cervix
• D Malignant melanoma of the cervix

Explanation

Small cell neuroendocrine carcinoma of the cervix shows small blue round cells with nuclear moulding, high mitotic activity and neuroendocrine markers such as synaptophysin, chromogranin and CD56. It behaves aggressively even at early stage and is associated with paraneoplastic syndromes including SIADH and ectopic ACTH production, explaining the severe hyponatraemia here. Melanoma would express S100, SOX10 and HMB45, not chromogranin.

Reference: Berek and Hacker's Gynecologic Oncology, 7th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.